LTE MIMO Antenna System for Automotive Carbon Fiber Rooftops

ABSTRACT

The present disclosure is related to an antenna system for a vehicle, such as a vehicle that has a non-metallic roof. The antenna system includes two metallic supports coupled to the roof. Additionally, the antenna system includes a first MIMO antenna pair. A first antenna of the first MIMO antenna pair is coupled to a first support of the two metallic supports, and a second antenna of the first MIMO antenna pair is coupled to a second support of the two metallic supports. The antenna system further includes a second MIMO antenna pair. A first antenna of the second MIMO antenna pair is coupled to the first support of the two metallic supports, and a second antenna of the second MIMO antenna pair is coupled to the second support of the two metallic supports. Yet further, the two metallic supports of the antenna system are physically separated from each other.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

With the advance of modern communication systems and vehiculartechnology, many vehicles contain cellular communication technology.Cellular communication technology may enable a vehicle to have bothvoice and data communication capabilities. To enable higher data rates,a communication system may use a Multiple Input, Multiple Output (MIMO)antenna system. A MIMO antenna system has more than one antennaconfigured to send and receive communication signals. In a MIMO antennasystem, it may be desirable for each antenna to operate uncoupled fromany other antenna of the MIMO system.

SUMMARY

Disclosed herein are examples that relate to an antenna system for usein vehicular system. In one aspect, the present application describes anantenna system for a vehicle, where the vehicle comprises a non-metallicroof. The antenna system includes a first metallic support coupled tothe roof. The antenna system also includes a first antenna coupled tothe first metallic support. The first metallic support forms a groundplane for the antenna and separates the first antenna from thenon-metallic roof.

In another aspect, the present application describes a method. Themethod includes forming a MIMO communication system for a vehicle. Thevehicle includes a non-metallic roof. The method further includestransmitting via a first antenna coupled to the first metallic groundplane a first electromagnetic communication signal. Additionally, themethod includes transmitting via a second antenna coupled to the secondmetallic ground plane a second electromagnetic communication signal.

In yet another example, an antenna system is provided. The antennasystem may be for a vehicle including a non-metallic roof. The antennasystem includes two metallic supports coupled to the roof. Additionally,the antenna system includes a first MIMO antenna pair. A first antennaof the first MIMO antenna pair is coupled to a first support of the twometallic supports, and a second antenna of the first MIMO antenna pairis coupled to a second support of the two metallic supports. The antennasystem further includes a second MIMO antenna pair. A first antenna ofthe second MIMO antenna pair is coupled to the first support of the twometallic supports, and a second antenna of the second MIMO antenna pairis coupled to the second support of the two metallic supports. Yetfurther, the two metallic supports of the antenna system are physicallyseparated from each other.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, examples, andfeatures described above, further aspects, examples, and features willbecome apparent by reference to the figures and the following detaileddescription.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an example layout of communication modules on avehicle.

FIG. 2A illustrates an example antenna.

FIG. 2B illustrates an example antenna.

FIG. 3A illustrates an example metallic support.

FIG. 3B illustrates two example metallic supports, each having twoantennas mounted.

FIG. 4 illustrates an example computing device for performing some ofthe methods disclosed herein.

FIG. 5 is an example method.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying figures, which form a part hereof. In the figures, similarsymbols typically identify similar components, unless context dictatesotherwise. The illustrative examples described in the detaileddescription, figures, and claims are not meant to be limiting. Otherexamples may be utilized, and other changes may be made, withoutdeparting from the scope of the subject matter presented herein. It willbe readily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

The following detailed description relates to an apparatus and methodsfor an antenna system for MIMO communication for use in vehicularsystem. The roof of a vehicle may be made of one or more differentmaterials, each of which may impact the performance of a MIMO antennasystem in different ways. For example, a vehicle may have a metallicroof. The metallic roof may function as a ground plane for the MIMOantenna system. However, a metallic roof may also cause coupling betweenantenna elements of the MIMO antenna system. In another example, thevehicle may have a carbon fiber (or other non-metallic) roof. The carbonfiber roof may act as an electronically lossy plane to which theantennas are mounted. The electronic properties of the carbon fiber roofmay cause the antenna(s) to have decreased performance. The antennaperformance decreased may include a decrease in impedance matching, adecrease in efficiency, a poor radiation pattern, or other performancedecreases. Therefore, it may be desirable to create an antenna systemthat can be used with a carbon fiber (or other non-metallic) roof, whilemaintaining sufficient antenna performance.

The presently-disclosed antenna system includes of a metallic support(described herein as a metallic tub) that covers at least a portion ofthe carbon fiber roof of the vehicle. The tub provides a metallic groundplane for the antenna's operation. Further, the metallic tub alsoreduces losses caused by the carbon fiber roof, thus increasing antennaperformance. The antennas may be mounted on the metallic tub.

Because the presently disclosed system may be used with a MIMO antennaconfiguration (i.e., an antenna configuration having more than oneantenna configured to send and receive communication signals), there maybe more than one antenna in the system. In order to achieve the bestMIMO performance, it may be desirable for the antennas of the MIMOsystem to be uncoupled and uncorrelated. In one example, each antenna ofthe MIMO system may be: (i) spaced such that the distance betweenantennas provides spatial diversity, (ii) aligned with a polarizationorthogonal to the other antennas of the MIMO system; and (iii) coupledto a different metallic tub than the other antennas of the MIMO system.By being physically separated by a distance, aligned orthogonally, andhaving a separate tub acting as the ground plane, the antennas may befurther uncoupled and uncorrelated.

In additional examples, the antenna system may be further configured tooperate with multiple wireless carriers via a MIMO antennaconfiguration. In these examples, each wireless carrier may have anassociated wireless transceiver (e.g. radio hardware or modem) on thecar (i.e., one wireless transceiver may be configured to communicatewith only one wireless carrier). Because each wireless carrier may havean associated wireless transceiver configured for MIMO communication, itmay be further desirable for each transceiver to be coupled to its ownrespective set of antennas. In one example, a vehicle may be configuredwith two wireless transceivers, each transceiver configured to operatein MIMO mode having two antennas. Therefore, the antenna system may havefour antennas total. As previously discussed, it is desirable for theantennas to be uncoupled and uncorrelated. However, the desire forantennas to be uncoupled and uncorrelated is primarily focused within asingle transceiver operation. Thus, in some examples, it is not criticalfor the two antennas of the present disclosure, operating with differenttransceivers, to be uncoupled and uncorrelated as if the two antennaswere operating with a single transceiver. However, in some alternateexamples, it is may be desirable for the two antennas of the presentdisclosure, operating with different transceivers, to be uncoupled anduncorrelated as if the two antennas were operating with a singletransceiver because the two transceivers may be operating in the samefrequency band.

In one example, the system may include 2 different LTE modems to servetwo different carriers (or, to provide redundancy for a single carrier),and each LTE modem may have 2 antennas for MIMO operation. The frequencyrange to be supported by the antennas and modems may be 698 to 960 MHzand 1710 to 2690 MHz. Thus, the antennas may each be dual-band antennas.The frequencies supported may be a superset of all the cellular bands,which may have challenges for designing antennas while maintaining thehigh efficiency, correlation, and coupling requirements.

FIG. 1 illustrates an example layout of communication modules 104 a and104 b for an autonomous vehicle 102. Each of the communication modules104 a and 104 b of the vehicle 102, may include a respective antennasystem for MIMO communication. As shown in FIG. 1, an autonomous vehicle102 may contain more than one communication module. For example, theautonomous vehicle 102 may have two communication modules 104 a and 104b mounted to the roof of the vehicle. However, a vehicle could include agreater or fewer number of communication modules.

Each communication module of the vehicle 102 may be configured with atleast one antenna and a metallic ground plane. As previously discussed,a roof of a vehicle may be made of carbon fiber, or another material,that may act as an electronically lossy plane. An electronically lossyplane can cause poor antenna performance when an antenna is mounted nearthe lossy plane. To mitigate the effects caused by the lossy plane, eachcommunication module may include a metallic ground plane upon whichantennas may be mounted. In some examples, the metallic ground plane maybe shaped to conform to the underlying roof structure of the vehicle. Inthese examples, the metallic ground plane may be tub shaped.

In some additional examples, all the communication modules of thevehicle may be configured with the same number of antennas. For example,each communication module may include two antennas. Additionally, thegeometry of the communication modules may change depending on thelocation of a respective communication module. For example, acommunication module located on the driver side of a vehicle may have ageometry that is mirrored from corresponding communication modulelocated on the passenger side of the vehicle.

The number of communication modules may be chosen based on a number ofcriteria, such as ease of manufacturing of the communication modules,vehicle placement, or other criteria. For example, some communicationmodules may be configured with a planar structure that is sufficientlysmall. The planar communication modules may be mountable at variouspositions on a vehicle. For example, a vehicle may have a dedicatedcommunication housing mounted on the top of the vehicle. Thecommunication housing may contain multiple communication modules.However, in other examples, communication modules may be placed withinthe vehicle structure.

When communication modules are located within the vehicle structure,each may not be visible from outside the vehicle without removing partsof the vehicle. Thus, in some examples, the vehicle may not be alteredaesthetically, cosmetically, or aerodynamically from addingcommunication modules. For example, communication modules may be placedunder vehicle trim work, such as under a roof covering, or otherlocations as well. In some examples, it may be desirable to placecommunication modules in positions where the object covering thecommunication modules is at least partially transparent toelectromagnetic energy. For example, various plastics, polymers, andother materials may form part of the vehicle structure and cover thecommunication modules, while allowing the electromagnetic signal to passthrough. Therefore, the antenna system may not be visible when thevehicle is viewed from outside as the vehicle's housing may cover thecomponents of the antenna system.

FIG. 2A illustrates three different view of an example antenna for usewith the methods and apparatuses described herein. The antenna can beseen in front view 200, side view 220, and bottom view 240. The antennaof FIG. 2A is one example antenna. Other antenna geometries may be usedbased on design criteria. The frequency range to be supported by theexample antenna may be 698 to 960 MHz and 1710 to 2690 MHz. Thus, theantenna may be a dual band antenna. However, in different examples, theantenna may be configured to operate with different (including more orfewer) frequency bands.

As shown in FIG. 2A, the antenna may include a feed 202. The feed 202may be configured to receive an electromagnetic signal from radiohardware for the antenna to radiate away from the vehicle. The feed 202may also be configured to couple a signal received by the antenna fromoutside of the vehicle to radio hardware for processing. The antenna mayalso include a plurality of spacers 204A-204C. The plurality of spacers204A-204C may be configured to both (i) provide a desired separationbetween the antenna and a metallic ground plane and (ii) provide animpedance matching for the antenna 200. The plurality of spacers204A-204C may also provide mechanical stability and robustness for theantenna. The plurality of spacers 204A-204C may prevent large movementsof the antenna while the vehicle is moving.

Additionally, the antenna may include a radiating portion 206. Theradiating portion 206 may be configured to cause a guidedelectromagnetic signal on the antenna to radiate away from the antennaas an unguided signal. Further, the radiating portion 206 may beconfigured to convert an unguided electromagnetic signal from outside ofthe vehicle to a guided signal on the antenna. Essentially, theradiating portion 206 may function to convert guided waves that arelocated in the vehicle's systems to unguided waves and vice versa.

FIG. 2B illustrates a three dimensional view of an example antenna 250for use with the methods and apparatuses described herein. The antennaof FIG. 2B may be similar to the antennas described with respect to FIG.2A, such as having dual-band operation.

As shown in FIG. 2B, the antenna 250 may include a feed 252, a pluralityof spacers 254A-254B, and a radiating portion 256. Because the antenna250 disclosed in FIG. 2B is similar to the antenna described withrespect to FIG. 2A, the various component of the antenna 250 mayfunction in a similar manner to those in FIG. 2B. As previouslydiscussed, the feed 252 may be configured to receive an electromagneticsignal from radio hardware for the antenna to radiate away from thevehicle and may also be configured to couple a signal received by theantenna from outside of the vehicle to radio hardware for processing.The plurality of spacers 254A-254B configured to both (i) provide adesired separation between the antenna and a metallic ground plane and(ii) provide an impedance matching for the antenna 250. The plurality ofspacers 254A-254B may also provide mechanical stability and robustnessfor the antenna. The plurality of spacers 254A-254B may prevent largemovements of the antenna while the vehicle is moving.

Although FIGS. 2A and 2B show a single geometry for an antenna. However,the present disclosure is in no way limited to the geometry, shape,type, or configuration of antenna shown in FIGS. 2A and 2B. One skilledin the art would be able to modify and substituted other antennas withinthe present disclosure.

FIG. 3A illustrates an example metallic support 300 for use with themethods and apparatuses described herein. The metallic support 300 mayserve multiple functions within the context of the present disclosure.One function of the metallic support 300 may be functioning as a groundplane on which antennas may be mounted. Additionally, another functionof the metallic support 300 may be providing a separation between anantenna and a non-metallic roof of the vehicle. In yet another function,the metallic support 300 may help to provide isolation between antennapairs (discussed further with respect to FIG. 3B below). Even further,the metallic support 300 may function to conform to the roof of thevehicle and may form a tub shape.

As previously discussed, a vehicle to which the metallic support 300 maybe mounted may have a carbon fiber (or other electromagnetically lossymaterial) roof. Without the metallic support 300, the carbon fiber roofwould act as an electromagnetically lossy plane and may cause theantenna(s) to have decreased performance. Therefore, by having ametallic support 300 mounted on the carbon fiber roof, the antenna mayhave an appropriate metallic ground plane for efficient antennaoperation.

The metallic support 300 may cover at least a portion of the carbonfiber roof of the vehicle. In some examples, the metallic support 300may be shaped to conform (or approximately conform) to the shape of theroof the vehicle. In other examples, the metallic support 300 may beshaped to fit in an area of the roof of the vehicle where some of thecarbon fiber has been removed. The metallic support 300 may take otherpossible shapes as well.

FIG. 3B illustrates a portion of two communication modules, eachincluding two example metallic supports 358A and 358B, each having twoantennas mounted 352A, 352B, 354A, and 354B. The two example metallicsupports 358A and 358B may form a portion of communication modules 104Aand 104B of FIG. 1, respectively. In one example, communication module104A of FIG. 1 may include metallic support 358A and two antennas 352A,354A. Additionally, communication module 104B of FIG. 1 may includemetallic support 358B and two antennas 352B, 354B. As shown in FIG. 3B,one communication module may include antennas that have an alignmentthat is reflected across a center axis of the car from the antennas ofthe other communication module. In one example, each communicationmodule may include a metallic support and two antennas. In some otherexamples, each communication module may have more or fewer antennas aswell.

The communication modules of FIG. 3B may form MIMO antenna pairs for usein a communication system. As previously discussed, a MIMO antennasystem has more than one antenna configured to send and receivecommunication signals. In a MIMO antenna system, it may be desirable foreach antenna to operate uncoupled from any other antenna of the MIMOsystem. The communication modules of FIG. 3B may aid in forming a MIMOcommunication system by providing both spatial and polarization basedantenna diversity. By providing both spatial and polarization diversity,the antennas that form a MIMO antenna pair may have antennas that arerelatively uncoupled and uncorrelated with each other. The MIMO antennapair may have radiation pattern diversity that are uncoupled anduncorrelated with each other.

In one example, a MIMO antenna pair include one antenna from each of thecommunication modules. A first MIMO antenna pair may include antennas352A and 354B. A second MIMO antenna pair may include antennas 352B and354A.

The communication modules of FIG. 3B provide spatial diversity due tothe antennas being physically separated from each other. For example, asshown in FIG. 1, the two communication modules may be located onopposite sides of the vehicle. Thus, the two antennas may be separatedby a distance that is close to the width of the vehicle. Additionally,the two metallic supports 358A and 358B of the communication modules maybe physically separate from each other as well. By having the metallicsupports 358A and 358B separate from each other, each communicationmodule may have its own respective ground plane. By having each antennaof a MIMO pair coupled to its own ground plane, the antennas may befurther isolated from each other to reduce coupling and correlation.

The communication modules of FIG. 3B provide radiation pattern diversitydue to the antennas of each MIMO pair being aligned orthogonally fromeach other. As first MIMO pair includes antennas 352A and 354B, theantennas may be aligned orthogonally (i.e. that is perpendicularly toeach other). Similarly, as the second antenna pair includes antennas352B and 354A, the antennas may be aligned orthogonally (i.e. that isperpendicularly to each other). Because the antennas of each MIMO pairare aligned orthogonally, the antennas of the MIMO pair will havediverse radiation patterns. Thus, the antennas will have uncorrelatedradiation pattern diversity due to their respective alignments.

In some examples, a computing device may implement some of the disclosedmethods as computer program instructions encoded on a non-transitorycomputer-readable storage media in a machine-readable format, or onother non-transitory media or articles of manufacture. For example, thecomputing device may be integrated within the radio hardware or it maybe a separate computing device in communication with the radio hardware.FIG. 4 is a schematic illustrating a conceptual partial view of anexample computer program product that includes a computer program forexecuting a computer process on a computing device, arranged accordingto at least some examples presented herein.

FIG. 4 illustrates a functional block diagram of a computing device 400,according to an examples. The computing device 400 can be used toperform functions in connection with an LTE MIMO Antenna System. Inparticular, the computing device can be used to perform some or all ofthe functions discussed above in connection with FIGS. 1-3. As shown inFIG. 4, the antennas 480 are located external to the computing device400.

The computing device 400 can be or include various types of devices,such as, for example, a server, personal computer, mobile device,cellular phone, or tablet computer. In a basic configuration 402, thecomputing device 400 can include one or more processors 410 and systemmemory 420. A memory bus 430 can be used for communicating between theprocessor 410 and the system memory 420. Depending on the desiredconfiguration, the processor 410 can be of any type, including amicroprocessor (μP), a microcontroller (μC), or a digital signalprocessor (DSP), among others. A memory controller 415 can also be usedwith the processor 410, or in some implementations, the memorycontroller 415 can be an internal part of the processor 410.

Depending on the desired configuration, the system memory 420 can be ofany type, including volatile memory (such as RAM) and nonvolatile memory(such as ROM, flash memory). The system memory 420 can include one ormore applications 422 and program data 424. The application(s) 422 caninclude an index algorithm 423 that is arranged to provide inputs to theelectronic circuits. The program data 424 can include contentinformation 425 that can be directed to any number of types of data. Theapplication 422 can be arranged to operate with the program data 424 onan operating system.

The computing device 400 can have additional features or functionality,and additional interfaces to facilitate communication between the basicconfiguration 402 and any devices and interfaces. For example, datastorage devices 440 can be provided including removable storage devices442, non-removable storage devices 444, or both. Examples of removablestorage and non-removable storage devices include magnetic disk devicessuch as flexible disk drives and hard-disk drives (HDD), optical diskdrives such as compact disk (CD) drives or digital versatile disk (DVD)drives, solid state drives (SSD), and tape drives. Computer storagemedia can include volatile and nonvolatile, non-transitory, removableand non-removable media implemented in any method or technology forstorage of information, such as computer readable instructions, datastructures, program modules, or other data.

The system memory 420 and the storage devices 440 are examples ofcomputer storage media. Computer storage media includes, but is notlimited to, RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, DVDs or other optical storage, magnetic cassettes, magnetictape, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to store the desired information and thatcan be accessed by the computing device 400.

The computing device 400 can also include output interfaces 450 that caninclude a graphics processing unit 452, which can be configured tocommunicate with various external devices, such as display devices 490or speakers by way of one or more A/V ports or a communication interface470.

The communication interface 470 can include a network controller 472,which can be arranged to facilitate communication with one or more othercomputing devices, via antennas 480, over a network communication by wayof one or more communication ports 474. The network controller may takethe form of radio hardware, such as a cellular modem configured forvoice and/or data communication. The communication connection is oneexample of a communication media. Communication media can be embodied bycomputer-readable instructions, data structures, program modules, orother data in a modulated data signal, such as a carrier wave or othertransport mechanism, and includes any information delivery media. Amodulated data signal can be a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia can include wired media such as a wired network or direct-wiredconnection, and wireless media such as acoustic, radio frequency (RF),infrared (IR), and other wireless media.

The communication interface 470 may include radio hardware configured toprovide a cellular radio connection. The cellular radio connection maybe able to provide a data and/or voice connection. In some furtherexamples, the radio hardware may also be configured to operate a MIMOantenna configuration. In yet another example, the radio hardware maycontain more than one modem. Each modem may be configured to operatewith a different network provider. Additionally, each modem may beconnected to its own respective MIMO pair of antennas. For example, aspreviously discussed, a vehicle may have four antennas configured intoto MIMO antenna pairs. Each MIMO antenna pair may be coupled to one ofthe two modems. Thus, each MIMO pair may be configured to be incommunication with only one network provider.

The computing device 400 can be implemented as embedded computinghardware within a vehicle. The various component of computing device 400may be located through a vehicle. The computing device 400 can also beimplemented as a personal computer including both laptop computer andnon-laptop computer configurations.

The one or more programming instructions can be, for example, computerexecutable instructions. A computing device (such as the computingdevice 400 of FIG. 4) can be configured to provide various operations inresponse to the programming instructions conveyed to the computingdevice by one or more of the computer-readable medium, the computerrecordable medium, and the communications medium.

FIG. 5 is an example method for communication with LTE MIMO antennasystem for automotive carbon fiber rooftops. Moreover, the method 500 ofFIG. 5 will be described in conjunction with FIGS. 1-4. A vehicularcommunication system may be configured to communicate over a wirelessnetwork, such as a cellular communication network. To communicate over awireless network, the communication system may transmit and receiveelectromagnetic signals. In order to achieve better communicationperformance, the communication system may contain multiple antennasconfigured as a MIMO antenna system. As previously discussed, a MIMOantenna system may use multiple antennas to both transmit and receivecommunication signals. However, because a vehicle may have a roof thatis non-metallic and electrically lossy, it may be desirable to provide anon-lossy ground plane for the antennas to improve their performance.

At block 502, the method 500 includes providing a first metallic groundplane coupled to the non-metallic roof. The first metallic ground planemay be similar to or the same as the metallic support discussed abovewith respect to FIG. 3A. The first metallic ground plane may be locatedon a side of the vehicle (e.g., the passenger or driver side).Alternatively, first metallic ground plane may be located on either thefront of the back of the vehicle.

As previously discussed, the first metallic ground plane may cover atleast a portion of the carbon fiber roof of the vehicle. The firstmetallic ground plane may be shaped to conform (or approximatelyconform) to the shape of the roof the vehicle. In other examples, thefirst metallic ground plane may be shaped to fit in an area of the roofof the vehicle where some of the carbon fiber has been removed. Forexample, in a regions where the first metallic ground plane is to coupleto the roof, a portion of the carbon fiber may be cut out, removed, orshaped in a way to allow the first metallic ground plane to couple tothe roof. The metallic support 300 may take other possible shapes aswell.

At block 504, the method 500 includes providing a second metallic groundplane coupled to the non-metallic roof. The second metallic ground planemay be similar to the first metallic ground plane provided at block 502.However, the second metallic ground plane may be mounted to the vehiclein a different location than the first metallic ground plane. Forexample, if the first metallic ground plane was mounted on the driver'sside, the second metallic ground plane may be mounted on the passenger'sside. Further, if the first metallic ground plane is be located on thefront of the vehicle, the second metallic ground plane is be located onthe back of the vehicle. Additionally, the first metallic ground planeand the second metallic ground plane may be physically separated fromeach other. By physically separating the first metallic ground plane andthe second metallic ground plane, electrical signals that are on oneground plane will not easily couple to the second ground plane.

At block 506, the method 500 includes, transmitting via a first antennacoupled to the first metallic ground plane an electromagneticcommunication signal having a first polarization. The first antenna maybe configured to receive an electromagnetic signal from a radio unit viaa first antenna feed. When the first antenna receives theelectromagnetic signal from the first feed, an electrical current may becreated on the surface of the first antenna. The electrical current onthe surface of the first antenna may cause the antenna to transmit (i.e.radiate) a signal into free space. Thus, the first antenna may convertan electromagnetic signal coupled into the first antenna feed into asignal radiating in free space away from the vehicle.

The first antenna may transmit the electromagnetic signal with a firstradiation pattern or polarization. The radiation pattern of thetransmitted electromagnetic signal is based on the orientation of therespective antenna in a MIMO pair. The polarization of the transmittedelectromagnetic signal is based on the direction which the electricalcurrent on the surface of the antenna flows. Thus, the orientation andthe geometry of the first antenna may dictate the radiation patternand/or polarization of the transmitted electromagnetic signal.

At block 508, the method 500 includes transmitting via a second antennacoupled to the second metallic ground plane an electromagneticcommunication signal having a second radiation pattern or polarization,wherein the second pattern or polarization is substantially diverse ororthogonal to the first antenna. The second antenna may be similar tothe first antenna. However, the second antenna may be coupled to adifferent metallic ground plane than the first antenna. Additionally,the second antenna may have a different orientation than the firstantenna.

Similar to the first antenna, the second antenna may also be configuredto receive and electromagnetic signal from a radio unit via a secondantenna feed. Further, when the second antenna receives theelectromagnetic signal from the second feed, an electrical current maybe created on the surface of the second antenna. The electrical currenton the surface of the second antenna may cause the antenna to transmit(i.e. radiate) a signal into free space. Thus, like the first antenna,the second antenna may convert an electromagnetic signal coupled intothe second antenna feed into a signal radiating in free space away fromthe vehicle.

Also similar to the first antenna, the second antenna may transmit theelectromagnetic signal with a second radiation pattern or polarization.Because the radiation pattern or polarization of the transmittedelectromagnetic signal is based on the direction which the electricalcurrent on the surface of the antenna flows, and the second antenna hasa different orientation than the first antenna, the second radiationpattern or polarization may be different than the first radiationpattern or polarization. In some examples, the first antenna and thesecond antenna may be aligned orthogonally with respect to each other.Thus, the electromagnetic signals radiated by each antenna with beorthogonal as well.

Therefore, due to the space between the antennas and the orthogonally ofthe polarizations, it may be possible to create a MIMO antenna pair ofantennas that provide both spatial and polarization diversity. Becausethe antennas that form a MIMO antenna pair may have both spatial andpolarization diversity, the antennas may function as if they arerelatively uncoupled and uncorrelated with each other. Therefore, method500 and the presently disclosed systems and apparatuses may be used tocreate a high performance MIMO antenna system mounted to an electricallylossy roof of vehicle.

In some cases a portion of the disclosed methods can be implemented ascomputer program instructions encoded on a non-transitorycomputer-readable storage medium in a machine-readable format, or onother non-transitory media or articles of manufacture. The computerprogram product includes a computer program for executing a computerprocess on a computing device, arranged according to some disclosedimplementations.

The computer program product is provided using a signal bearing medium.The signal bearing medium can include one or more programminginstructions that, when executed by one or more processors, can providefunctionality or portions of the functionality discussed above inconnection with FIGS. 1-3 and FIG. 5. In some implementations, thesignal bearing medium can encompass a computer-readable medium such as,but not limited to, a hard disk drive, a CD, a DVD, a digital tape, ormemory. In some implementations, the signal bearing medium can encompassa computer-recordable medium such as, but not limited to, memory,read/write (R/W) CDs, or R/W DVDs. In some implementations, the signalbearing medium can encompass a communications medium such as, but notlimited to, a digital or analog communication medium (for example, afiber optic cable, a waveguide, a wired communications link, or awireless communication link). Thus, for example, the signal bearingmedium can be conveyed by a wireless form of the communications medium(for example, a wireless communications medium conforming with the IEEE802.11 standard, cellular communication standards, or other transmissionprotocols).

It should be understood that arrangements described herein are forpurposes of example only. As such, those skilled in the art willappreciate that other arrangements and other elements (e.g. machines,apparatuses, interfaces, functions, orders, and groupings of functions,etc.) can be used instead, and some elements may be omitted altogetheraccording to the desired results. Further, many of the elements that aredescribed are functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in anysuitable combination and location.

While various aspects and examples have been disclosed herein, otheraspects and examples will be apparent to those skilled in the art. Thevarious aspects and examples disclosed herein are for purposes ofillustration and are not intended to be limiting, with the scope beingindicated by the following claims.

What is claimed is:
 1. An antenna system for a vehicle, wherein thevehicle comprises a non-metallic roof, comprising: a first metallicsupport coupled to the roof; and a first antenna coupled to the firstmetallic support, wherein the first metallic support forms a groundplane for the antenna and separates the first antenna from thenon-metallic roof.
 2. The antenna system according to claim 1, furthercomprising: a second metallic support coupled to the roof; a secondantenna coupled to the second metallic support, wherein the secondmetallic support forms a ground plane for the second antenna andseparates the second antenna from the non-metallic roof.
 3. The antennasystem according to claim 2, wherein a polarization of the first antennais orthogonal to a polarization of the second antenna.
 4. The antennasystem according to claim 2, wherein the first metallic support and thesecond metallic support are physically separated from each other.
 5. Theantenna system according to claim 2, wherein the first antenna and thesecond antenna form a MIMO antenna pair.
 6. The antenna system accordingto claim 2 further comprising: a third antenna coupled to the firstmetallic support; and a fourth antenna coupled to the second metallicsupport, wherein the third antenna and the fourth antenna form a MIMOantenna pair.
 7. The antenna system according to claim 6, wherein apolarization of the third antenna is orthogonal to a polarization of thefourth antenna.
 8. The antenna system according to claim 1, wherein aradiation pattern of the first antenna is orthogonal to a radiationpattern of the second antenna.
 9. The antenna system according to claim1, wherein the first antenna is configured as a dual band antenna.
 10. Amethod, comprising: transmitting via a first antenna coupled to a firstmetallic ground plane a first electromagnetic communication signal; andtransmitting via a second antenna coupled to a second metallic groundplane a second electromagnetic communication signal, wherein the firstand second metallic ground planes and disposed on a non-metallic roof ofa vehicle.
 11. The method of claim 10, wherein: the firstelectromagnetic communication signal is transmitted having a firstpolarization; and the second electromagnetic communication signal istransmitting having a second polarization, wherein the secondpolarization is substantially orthogonal to the first polarization. 12.The method of claim 10, wherein the first metallic support and thesecond metallic support are physically separated from each other. 13.The method of claim 10, wherein the first antenna and the second antennaform a MIMO antenna pair.
 14. The method of claim 10, furthercomprising: transmitting via a third antenna coupled to the firstmetallic ground plane a third communication signal; and transmitting viaa fourth antenna coupled to the second metallic ground plane a fourthcommunication signal, wherein the third antenna and the fourth antennaform a MIMO antenna pair.
 15. The method of claim 14, wherein apolarization of the third antenna is orthogonal to a polarization of thefourth antenna.
 16. The method of claim 10, wherein the firstelectromagnetic communication signal is transmitted having a firstradiation pattern; and the second electromagnetic communication signalis transmitting having a second radiation pattern, wherein the secondradiation pattern is substantially orthogonal to the first radiationpattern.
 17. An antenna system for a vehicle, wherein the vehiclecomprises a non-metallic roof, comprising: two metallic supports coupledto the roof; a first MIMO antenna pair, wherein: a first antenna of thefirst MIMO antenna pair is coupled to a first support of the twometallic supports; and a second antenna of the first MIMO antenna pairis coupled to a second support of the two metallic supports; and asecond MIMO antenna pair, wherein: a first antenna of the second MIMOantenna pair is coupled to the first support of the two metallicsupports; and a second antenna of the second MIMO antenna pair iscoupled to the second support of the two metallic supports; and whereinthe two metallic supports are physically separated from each other. 18.The antenna system according to claim 17, wherein for each MIMO antennapair, a polarization of the first antenna is orthogonal to apolarization of the second antenna.
 19. The antenna system according toclaim 17, wherein for each MIMO antenna pair, a radiation pattern of thefirst antenna is orthogonal to a radiation pattern of the secondantenna.
 20. The antenna system according to claim 17, wherein themetallic support conforms to contours of a region of the non-metallicroof.